The work proposed is aimed at the elucidation of the mechanisms of thermal reactions. The stereochemistry of such processes will suggest the geometry of the transition state and hence the nature of the molecular motions involved in the reaction coordinate. The specific processes under study include thermal rearrangements and cycloadditions. The properties of diradicals are being explored by an examination of the chemistry of trimethylenemethanes. The studies have health relevance because of their implications for the synthesis of biologically active molecules.